Ultrastructure of an unidentified microsporidium from the convergent lady beetle, Hippodamia convergens Guérin-Méneville

Abstract

An unidentified microsporidium was found in adult Hippodamia convergens Guérin-Méneville that were obtained from a commercial insectary for aphid biological control. Ultrastructure of the microsporidium was examined by transmission electron microscopy. All stages of the microsporidium were diplokaryotic and the pathogen developed in direct contact with host cell cytoplasm. Two morphologically distinct spores were observed. The first type had a thin exospore, thickened endospore, and typical internal spore structures. The second spore type was atypical in appearance, lacking any discernable internal structures. Typical and atypical spores measured 3.5 ± 0.2 x 2.06 ± 0.19 μm ( n = 10) and 3.38 ± 0.8 x 2.13 ± 0. 16 μm ( n = 10), respectively. Based on spore dimensions and pathogen ultrastructure, the results of this study indicate that the microsporidium in question is likely Nosema hippodamiae Lipa & Steinhaus. Further evidence based on molecular techniques is required for continuation.